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Question: Answered & Verified by Expert
A metal crystallizes into two cubic systems-face centred cubic (fcc) and simple cubic (SC), whose unit cell lengths are 4.5 and 1.5 A o respectively. Calculate the ratio of densities of face centred cubic and Simple cubic.
ChemistrySolid StateJEE Main
Options:
  • A 0.15
  • B 1.44
  • C 2.25
  • D 3.25
Solution:
2254 Upvotes Verified Answer
The correct answer is: 0.15
face centred cubic unit cell length =4.5 A o
Simple cubic unit cell length =1.5 A o
Density in face centred cubic =n1×atomic   weightV1×Avogadro   number
Density simple cubic (SC) =n2×atomic    massV2×Avogardro   number
DfccDbcc=n1n2×V2V1
n1 for face centred cubic = 4; Also V1=a3=4.5×10-83
n2 for simple cubic = 1; Also V2=a3=1.5×10-83
DfccDsc=4×(1.5×10-8)31×(4.5×10-8)3=0.15

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